Field of the Invention
The present invention relates to a liquid crystal display and a multi-screen display.
Description of the Background Art
Generally, in a case of a multi-screen display which configures a large screen display by using a plurality of liquid crystal displays, the multi-screen display is configured by combining a plurality of liquid crystal displays using an LCD (Liquid Crystal Display) with a size of about 40 to 60 inches. Conventionally, a CCFL (Cold Cathode Fluorescent Lamp) has been used as a light source of the liquid crystal display using the LCD. However, in recent years, a light source which configures a backlight to illuminate an LCD panel from a back surface by disposing a plurality of LEDs (Light Emitting Diodes) directly below the liquid crystal panel has been the mainstream. In a video image display part of the liquid crystal display, a diffusion sheet and a diffusion plate are disposed on the back surface of the liquid crystal panel, and light of the backlight transmitted through the diffusion sheet and the diffusion plate configures an image of a liquid crystal module. The LED light source used for the backlight is basically disposed inside a backlight housing of the liquid crystal panel, and a reflection sheet is disposed on a back surface side of the LED light source. All of these configuration members are covered with a sheet metal. Further, a panel driving substrate or the like is disposed on a back surface of the sheet metal, and the substrate and an internal LCD module are unitized as a liquid crystal panel module in a state in which they are connected by a lead wire.
When a large screen is configured, luminances of the plurality of liquid crystal displays which configures the large screen must be uniform. Accordingly, it is necessary to detect the luminance of each individual liquid crystal display. As the detection method, there is a method of detecting light transmitted through a reflection sheet disposed on a back surface of an LED light source (see Japanese Patent Application Laid-Open No. 10-222084 (1998)).
In Japanese Patent Application Laid-Open No. 10-222084 (1998), a photodetector detects the light transmitted through the reflection sheet disposed on the back surface of the LED light source. However, in the liquid crystal display in recent years, since a reflectance of the reflection sheet has been improved, the light transmitted through the reflection sheet does not have a detectable intensity.